diff --git a/lantern_scripts/combine.py b/lantern_scripts/combine.py
index 7c2035113..cdb3bc758 100755
--- a/lantern_scripts/combine.py
+++ b/lantern_scripts/combine.py
@@ -71,7 +71,8 @@ if __name__ == "__main__":
         well_addr = str(well_addr)
 
         hdr_well_image = cv2.imread(well_addr,  cv2.IMREAD_UNCHANGED)
-        hdr_fast_image = cv2.imread(well_addr.replace(args.well_dir, args.fast_dir), cv2.IMREAD_UNCHANGED)
+        if args.fast_dir is not None:
+            hdr_fast_image = cv2.imread(well_addr.replace(args.well_dir, args.fast_dir), cv2.IMREAD_UNCHANGED)
 
 
         # hdr_well_image = np.uint8(hdr_well_image * 255.0)
@@ -79,7 +80,9 @@ if __name__ == "__main__":
         
         if args.do_linearization:
             hdr_well_image = apply_correction((camera_data["b"], camera_data["g"], camera_data["r"]), np.array(hdr_well_image), CORRECTION_CURVE_TYPE)
-            hdr_fast_image = apply_correction((camera_data["b"], camera_data["g"], camera_data["r"]), np.array(hdr_fast_image), CORRECTION_CURVE_TYPE)
+                
+            if args.fast_dir is not None:
+                hdr_fast_image = apply_correction((camera_data["b"], camera_data["g"], camera_data["r"]), np.array(hdr_fast_image), CORRECTION_CURVE_TYPE)
 
 
         # well_mask_addr = well_addr.replace('/well_expo/', '/well_mask/')
@@ -88,15 +91,21 @@ if __name__ == "__main__":
         # well_mask = well_mask.astype(np.float32) / 255.0
         # well_mask[well_mask > 0.1] = 1.0
 
-        weights_well = cut_weighting_function(hdr_well_image, WELL_EXPOSURE)
-        weights_fast = cut_weighting_function(hdr_fast_image, FAST_EXPOSURE)
+        
+        if args.fast_dir is not None:
+            weights_well = cut_weighting_function(hdr_well_image, WELL_EXPOSURE)
+            weights_fast = cut_weighting_function(hdr_fast_image, FAST_EXPOSURE)
 
         # fast_mask = cv2.imread(well_mask_addr.replace('/well_mask/', '/fast_mask/'))
         # fast_mask = fast_mask.astype(np.float32) / 255.0
 
         # final_output = weights_well * (hdr_well_image / WELL_EXPOSURE) + weights_fast * (hdr_fast_image / FAST_EXPOSURE)
         # final_output = final_output / (weights_well+weights_well)
-        final_output = weights_well * (hdr_well_image / WELL_EXPOSURE) + (hdr_fast_image / FAST_EXPOSURE)
+        
+        if args.fast_dir is not None:
+            final_output = weights_well * (hdr_well_image / WELL_EXPOSURE) + (hdr_fast_image / FAST_EXPOSURE)
+        else:
+            final_output = hdr_well_image / WELL_EXPOSURE
         # final_output = weights_well * (hdr_well_image / WELL_EXPOSURE)
 
         output_addr = well_addr.replace(args.well_dir, args.out_dir)